This application claims the priority of Korean Patent Application No. 2002-71972, filed on Nov. 19, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a micromirror actuator and a method of manufacturing the same and, more particularly, to a micromirror actuator that prevents a micromirror from being deformed and includes a reflective surface having improved roughness and flatness, and a method for manufacturing the same.
2. Description of the Related Art
Micromirror actuators are generally used in optical switches, image displaying devices, and the like. In order to operate an optical switch or an image displaying device, a micromirror actuator pivots several micromirrors supported on some substrates by using electrostatic forces selectively to change an optical path of incident light.
A micromirror actuator 10 using electrostatic forces will be described with reference to FIGS. 1 and 2. A trench 5 is formed in a substrate 15. A pair of support posts 20 vertically protrude from the upper surface of the substrate 15 beside either side of the trench 5. A micromirror 30 is placed between the pair of support posts 20. A pair of torsion bars 25 are connected to the micromirror 30 and the pair of support posts 20. Thus, the micromirror 30 is supported by the pair of torsion bars 25 to be capable of pivoting.
The micromirror 30 includes a driving portion 30a that faces the trench 5 when the micromirror 30 is horizontal and a reflecting portion 30b that is opposite to the driving portion 30a and reflects incident light.
A lower electrode 37 is formed on the bottom of the trench 5 and a side electrode 40 is formed on a sidewall of the trench 5. Electrostatic forces are generated between the lower electrode 37 and the driving portion 30a and between the side electrode 40 and the driving portion 30a so as to drive the micromirror 30. In other words, the electrostatic force between the lower electrode 37 and the driving portion 30a acts to pivot the micromirror 30 downward. After the micromirror 30 pivots to some extent, the electrostatic force between the driving portion 30a and the side electrode 40 acts so that the micromirror 30 continues to pivot and reaches an upright position. The micromirror 30 is elastically supported by the torsion bars 25 so as to be capable of pivoting. When the electrostatic forces are released, the micromirror 30 returns to the horizontal state due to the returning force of the torsion bars 25.
A process of manufacturing a micromirror of the micromirror actuator having the above-described structure will now be described. The trench 5 is formed in the substrate 15. The resultant structure is coated with a photoresist (not shown) to a predetermined thickness and an aluminum film forming the micromirror 30 is deposited thereon. Thereafter, the photoresist is removed to complete the micromirror structure. Here, a plurality of holes 31 are formed in the reflecting portion 30b in order to reduce the time required for removing the photoresist.
In the micromirror actuator having the above-described structure, light is lost via the holes 31.
In the process of manufacturing the micromirror actuator, as shown in FIG. 3, the aluminum film is deformed due to a stress remaining in the aluminum film when being deposited and heat generated by plasma when removing the photoresist. In order to solve this problem, in the prior art, a micromirror is made thicker in order to increase the stiffness of the micromirror. In this case, it is very difficult to reduce the deformation of the aluminum film due to a limitation in the deposition thickness of the aluminum film of the micromirror.